1. Field of the Disclosure
The present disclosure relates to a leakage current monitoring apparatus, and particularly, to a leakage current monitoring apparatus which monitors a resistive component leakage current harmful to a human body in a leakage current in association with a transformer-less photovoltaic (abbreviated as “PV” hereinafter) inverter connected to a grid.
2. Background of the Disclosure
In generating PV electric power, the electric power is generated by using an array of a PV module, and a type of power generated from the array of the PV module is direct current (abbreviated as “DC” hereinafter). Therefore, in order to supply generated electric power to a source of demand such as home or a company, it is required to convert the DC electric power into alternating current (abbreviated as “AC” hereinafter) electric power.
FIG. 1 illustrates an example of a grid-tied PV power generation system 10.
The grid-tied PV power generation system 10 may include PV module 11, an inverter 12, and a grid 13. The PV module 11 generates DC electric power by using sunlight, and the generated electric power is converted into AC electric power through the inverter 12 and is transferred to the grid 13.
Efficiency and stability should be considered when generating electric power with sunlight.
The inverter 12 may be categorized into an inverter, which is electrically insulated by a transformer, and a transformer-less inverter that does not include a transformer. Recently, the transformer-less inverter having advantages in terms of conditions such as efficiency, price, volume, and weight is attracting much attraction. However, a leakage current can severely occur in the transformer-less inverter that does not include the transformer.
In FIG. 1, fault conditions of a PV+ terminal or a PV− terminal of the PV module 11 are illustrated.
When a leakage current occurs, a resistive component R and a capacitive component C may exist between an electrical line and the earth. In this case, a leakage current caused by the capacitive component C is a value which always exists due to a characteristic of the PV module 11, and is not a component harmful to a human body. A leakage current caused by the resistive component R is a harmful component capable of affecting creature such as plants as well as human bodies.
Therefore, it is required to respond to a resistive component leakage current when using the transformer-less inverter.